Vulnerability DatabaseCVE-2022-27924

CVE-2022-27924:
Zimbra Collaboration Server vulnerability analysis and mitigation

Overview

Zimbra Collaboration (aka ZCS) versions 8.8.15 and 9.0 contained a high-severity vulnerability (CVE-2022-27924) that allowed an unauthenticated attacker to inject arbitrary memcache commands into a targeted instance. The vulnerability was discovered by SonarSource researchers in March 2022 and patched by Zimbra in May 2022 with versions 8.8.15 Patch 31.1 and 9.0.0 Patch 24.1 (Sonar Blog, Zimbra Advisory).

Technical details

The vulnerability arose from improper escaping of newline characters in untrusted user input before constructing Memcached commands. This allowed attackers to inject arbitrary commands into the Memcached protocol stream. When exploited, the vulnerability caused an overwrite of arbitrary cached entries, as the injected memcache commands became unescaped. The vulnerability received a CVSS v3.1 base score of 7.5 HIGH (Vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N) (NVD, CISA Advisory).

Impact

When successfully exploited, an attacker could steal cleartext email account credentials from users of a targeted Zimbra instance without requiring any user interaction. In environments not enforcing multifactor authentication (MFA), the stolen credentials could be used for spear phishing, social engineering, and business email compromise (BEC) attacks. Additionally, attackers could use the credentials to deploy webshells and maintain persistent access (CISA Advisory).

Mitigation and workarounds

Organizations were strongly advised to upgrade to Zimbra versions 8.8.15 Patch 31.1 or 9.0.0 Patch 24.1 or later. Additional recommended mitigations included blocking internet traffic to Zimbra servers where possible and configuring Zimbra to block external Memcached access, even on patched versions. Organizations that did not immediately patch upon release were advised to assume compromise and hunt for malicious activity (CISA Advisory).

Community reactions

Due to the severity and active exploitation of the vulnerability, CISA added CVE-2022-27924 to its Known Exploited Vulnerabilities Catalog on August 4, 2022, requiring federal agencies to patch by August 25, 2022 (CISA Advisory).